I think the purge was for two reasons: first, Quinn. He had to be handled very carefully and his reps monitored and practice time limited due to ongoing health issues. Second, his contract was quite large. Third, he just didn't fit Wade's profile for an OLB.
As far as Ogletree; big contract, poor tackler. Wade wants a guy who can stack and shed in the middle, and Ogletree either can't or won't. Not a good fit.
I really don't think the Rams are in as urgent a mode to extend Donald as people think. I think they're going to slow roll him, and keep him as cheaply as possible as long as possible......and then goodbye. That's kind of ruthless, but that's the business. Making Donald happy falls way down the to-do list.